The Key that Binds Us
by wordsofawitheringwriter
Summary: Earth Land is dying. The Erlking are rising. At the height of the war, an unconscious and dying Natsu is unknowingly thrust into a celestial portal by his friends in a last-ditch effort to save him. It'll take an old lighter and the remains of a rusted key to get him home, but with his travel cost him his memories. How does one get home when they don't know they're missing? Nalu
1. Prologue

**full summary:** _at the height of the war, an unconscious and dying Natsu is unknowingly thrust into a celestial portal by his friends in a last-ditch effort to save him._

 _he lives a normal life in this new world, no knowledge of the mage he once was, until one day unearthing a strange box that holds nothing but an old lighter and the remains of a rusted key._

 _what he finds shortly after is a world unlike his own, known as Fiore. He soon learns that something terrible has happened in this once calm land, and it's up to him to see that everything is made right again. The first step is believing, and the second step requires figuring out just what he's done to piss off a blonde girl he's never even met before. Or has he?_

* * *

 **Prologue I**

 _She had to keep her eyes on the path ahead, or she would never make it._

"Lay down cover! Hold them off for as long as you can!"

She swallowed hard and braced herself, holding out a hand to stop the sound of beating footsteps against the stone path as they ran through the heart of town, heading towards the little house at the edge of East Forest. She waited long enough to tune out the sounds of her friends' pants as the air crackled with the magic they were keeping at their fingertips.

She closed her eyes and listened for the sounds of the beasts hunting them.

They were coming for her, for her friends… they were coming for _him_. They wanted him, the figure lying on the hastily-made steel stretcher that was padded down with an old winter jacket. His body was wrapped from head to toe in an attempt to hide that infamous shade of hair that the beasts could spot easily overhead. He was motionless; no longer did his chest rise and fall beneath the cocoon of wool and thread. She tore her eyes away when the coat began to resemble a body bag.

They were running out of time.

"We have to keep moving!" she shouted, taking command as the first shriek rang out. Shadowy figures began to seep upwards from the cracks in the earth. They consisted of large, billowing plumes of soot and dust and the crackling of something sinister; the Black Fog.

Lucy heard the person flanking her right scoff, and could sense the irritation in Erza's voice growing as she said, "We can't outrun it. They're catching up!"

They had to hurry. From what they had gathered over the months since Earth Land first showed signs of dying, the fog meant the Erlking were zeroing in on their prey. Lucy cracked her whip in an attempt to disperse the cloud that was circling her feet while her friends argued amongst themselves.

"We need Laxus' lightning!"

" _You weren't there!_ The light does nothing to it! Laxus is better off where he is now, looking after the guild."

 _Or what's left of it,_ Lucy found herself guiltily thinking. She bit her lip and gripped the handle of her whip hard enough to turn her knuckles white as she cast one last glance at the body of Fairy Tail's Salamander.

Being the shortest, Wendy began to cough as the Black Fog reached her nostrils first. Lucy turned her head in time to see Gajeel scoop her up and onto his back, where the girl wrapped her arms tightly around his neck and hid her face there.

Lucy's eyes met Happy's swimming ones as he and Carla coasted above the group at a safe distance from the dark, swirling mist.

"Happy! Carla!" she called. "Take the stretcher on up ahead! We're right behind you!"

The Exceeds nodded their salutes, and as they swooped in just long enough to grab hold of either end of the stretcher, Lucy found herself having to hold her tongue from murmuring a last goodbye to the boy on it.

Her heart clenched painfully, constricting and calling out for him as the Exceeds disappeared over the top of the treeline bordering the edge of town.

 _Natsu, I'm coming. Hold on._

Taking a quick look at their dwindled numbers, a plan quickly began to formulate. The last few months have had to make them all quick on their feet.

"Gray! Erza! Can you hold off the Erlking on your own?"

The Erlking; creatures with bodies slick with light that hurled themselves through the air with thick, leathery wings that had been bonded to their bodies with a magic darker than the pits of their eyes.

Erza's jaw set with new determination as her eyes searched the sky. "Long enough for you to gain some distance."

Gray nodded in agreement, shouting for them to go on ahead when a burst of light very briefly dispersed a small section of the shadows as a result of Erza's requip.

"Run," Erza said, smiling gently at Lucy's lingering figure even after getting unwavering confirmation from both her and Gray. "We've already said our goodbye's to him, Lucy. We'll meet up with you all later." Inhaling a stuttering breath that laid heavily inside her, Erza bid her friends goodbye. "Now go, and make sure he's safe."

With tears in her eyes Lucy nodded, turning away from the pair to race after Gajeel who had already sprinted through the remaining alleyways separating them from the treeline when given the greenlight to get Wendy the hell away from the Black Fog. Together the trio fled from the cobblestone pathway of town with the sounds of " _Ice-Make-_ " and " _Requip_!" as their send off.

* * *

 **Until Next Time...**


	2. Part I: The Beginning

_Summary: Earth Land is dying. The Erlking are rising. At the height of the war, an unconscious and dying Natsu is unknowingly thrust into a celestial portal by his friends in a last-ditch effort to save him. It'll take an old lighter and the remains of a rusted key to get him home, but with his travel cost him his memories. How does one get home when they don't know they're missing? Nalu_

* * *

 **Part I: The Beginning**

 _The heat had always bothered him._

Natsu went up for a layup, already beginning to feel that he was sweating through his cutoff tee. His shoes were rubbing blisters where his socks were rubbing thin.

 _Ever since he could remember, he'd never been one to handle warmer temperatures._

He kept his weight light, shifting from one foot to the other to prevent the soles of his sneakers from melting to the blacktop as he caught the ball that slid smoothly through the torn net. Around him it was quiet; the school playground behind his house empty for the summer months. The air was dry with not a cloud in the sky to soften the sun's rays.

 _Just one glance at the scar on his upper left arm and you would know that he and fire had never mixed._

Drops of sweat began to collect at the top of his brow and at the base of his neck, causing the hair there to stick to his skin as he raised off the ground to attempt a three. The ball bounced once, twice, three times on the pavement after knicking the rim.

His palms slapped his knees as he doubled over to catch his breath. From the corner of his eye he could see the ball roll until coming to a soft stop at the edge of grass that bordered the asphalt. Natsu took in a deep breath through his nose, held it, then let it out in a heavy, drawn out sigh.

 _The heat had always bothered him._

He straightened up and crossed the court to where he left his bag on the wooden bench beneath a large oak. Igneel had nagged him enough over the years to to where he never forgot to bring a bottle of water with him, and as he rummaged for it, he felt his phone go off and illuminate the inside of his bag.

The text was from Gray: _where the hell are you?_

Natsu checked the time and cursed. He was going to make them late for work.

 _Sorry_ , he typed. _At the court. Lost track of time. On way._

He threw the straps of his bag over one shoulder and sprinted toward the treeline that separated his house from the playground, scooping up the ball as he went.

Waiting for him in the driveway was Gray, his Jeep running. Natsu hurried into the house just long enough to grab his workboots and drop his bag on his bed before finding himself out the door again.

"We're driving there with the windows down," Gray said as Natsu's seatbelt clicked into place. "You _reek_."

"Can it and drive," Natsu replied, flipping him a lazy bird, "or I'll tell Igneel you decline his next batch."

Gray mumbled a curse as he jerked them in a hard reverse out of the driveway. "Damn that man and his spicy jerky."

Natsu wrinkled his nose as they flew down the road, the trees soon giving way to interstate. He and Gray were working a summer job with a landscaping company that took them anywhere from down the street to several counties over. The current project had them working roughly an hour down the main highway where a quarry had once been, before the water was removed and the land graded over so that they could be contracted. Several years had passed in the time it took for everything to be approved, however, so some people had used the downtime as a place to throw their trash. It was a work in progress for sure, but the job paid well and the hours were decent. The only downside was the occasional long commute, in which he and Gray would carpool to save on gas.

"I don't know how you guys can eat that stuff," Natsu shuddered. "It's like eating straight fire."

Gray snorted. "Like you would know what that's like."

"Excuse me for not wanting my tongue to taste like charcoal."

His friend had merely rolled his eyes and flipped on the blinker, coasting over into the fast lane to make up for lost time. The rest of the ride consisted of Natsu playing with the radio and Gray complaining about the stations he chose, and Natsu staring out the window to keep from getting carsick.

He stuck his arm out to feel the air at one point when traffic landed them in a near standstill. Clouds had gathered and Natsu wondered if he was only imagining the static charge in the air while Gray cursed their bad luck.

A storm was coming.

* * *

Natsu's foster dad was a worrier. He hovered, was constantly checking and rechecking the expiration dates of everything in the fridge, and would text Gray asking if they had made it places when Natsu would forget or leave him on read.

It wasn't really his fault. Natsu couldn't remember much about the years of his life before coming to live with Igneel, but he knew the mother hen act was a result of hearing about the accident that had led Natsu to his front door.

That aside, Igneel seemed to have no problem allowing his son to spend hours outdoors under the sun doing hard labor.

" _It does a young man well to get out there,"_ he'd say. " _Put some hair on your chest. Rough up those hands. Some hair on your b-"_ but by this point he would normally be cut off by Natsu chucking the nearest object at his old man's head.

Now, looking up at the pale sky with its overlapping clouds that billowed out into deeper patches of gray, he could at least be thankful that the sun was no longer beating down on him.

But with dirt caked under his nails and the rough handle of a cheap shovel rubbing against torn callouses and open blisters through his gloves, that was about as far as his thanks would go.

The boy digging beside him grunted, shoving the head of his shovel into the dirt so that it stood upright; as good a stopping point as any. He was taller than Natsu and a few years older, if he wasn't mistaken. His hair was ruddy and flew in different directions, and his glasses always sat awkwardly on his crooked nose that had been broken at one time but never set properly. "I'm off to take my break," he nodded to Natsu. "You coming?" Lewis was his name.

Natsu waved him on ahead and continued his work, praying for rain so they could all be dismissed for the day. Even then, however, he doubted that he'd be so lucky. Boss was a decent guy who paid his workers fair, but he was also a man who liked to exceed any and all expectations. If he promised a client that a job would be done in a week's time, then by golly it would be done in half that. He was like Igneel; he thought the work was honest and built character and was not a leading cause of scoliosis.

Natsu was distracted from his thoughts when his shovel hit something that made a _ting_ and most certainly wasn't dirt. He mumbled a curse when the action jolted his bones after all his weight fell on whatever it was that some moron had planted there.

He huffed and tossed the shovel to the side, dropping to his hands and knees to brush the dirt away.

The first drops of rain began to fall as he unearthed the brass box that was tarnished from years spent beneath the soil. It wasn't large, just barely larger than his palm. He turned it over in his hands a few times and heard the contents shift around beneath the lid, but he soon discovered that opening it was futile at the moment. It was sealed tight.

He brushed some of the loose dirt aside to get a better look at the detailed etching. The carefully crafted indentions were packed with dirt and made it difficult to make out, but he ran his thumb along the design and had the strange sensation that it should feel familiar.

A crack of thunder clapped overhead. Natsu faintly registered the sounds of different conversations around him as others left their posts to seek shelter, but he remained on his knees by the small hole he'd created that had housed the small box. He sat, lost in thought as he grazed his thumb over the etching. The rain was slowly turning the dirt into mud that was easier to wipe away with the heel of his hand and the hem of his shirt.

He squinted at the faint lines, trying to figure out what it was supposed to be. It held a small resemblance to a type of bird, but he was at a loss as to what kind it could be. It certainly looked unlike any bird Natsu had ever seen.

"Natsu! Come on, man!" He was suddenly yanked to his feet by the collar of his shirt and dragged to the overhang where the rest of the guys were taking their breaks and cracking open lunch sacks.

"What the hell, dude?" Gray panted, and only now that he was out of the rain did Natsu feel wet. Soaked, actually. His bones were being washed clean by the rain water as he stood there shivering with the box safe in his hand. Gray had yet to notice it; too preoccupied with his friend's impression of a lighting rod, but Lewis did.

"Yo," the older boy said, raising to his feet. He tried to adjust his glasses, but they remained off-centered. "What's that in your hand?"

"I found it," Natsu replied. "Right after you left."

Someone that Natsu had never spoken to before asked, "Well? What's in it?"

"It's probably his time capsule," his buddy retorted, elbowing his friend in the ribs as the two cackled.

"I don't know yet," Natsu responded, ignoring the two strangers. "Doesn't open."

Lewis grinned, his canines sharp. "Everything with a seal can be opened, my friend."

Someone snatched the box from his hands before Natsu could decipher the boy's words.

"Give it back," Natsu growled, lunging for the man who had made the joke at his expense and was more than a few years Natsu's senior.

"We'll give it back," he chortled, "just as soon as we find out what's in it." He tutted at the sight of Natsu's balled fists. "You wouldn't want to keep all the treasures for yourself, now, would ya?"

"Yes," Natsu replied simply.

The man threw his head back and laughed as though it was the funniest joke he'd ever heard.

"Rimmer!" he yelled, cupping the side of his mouth with a large, meaty hand so that Natsu could see fat fingers and several scars etched into the sun-stained skin. "Get your tools so we can crack this baby open!"

Thunder drowned out the cheers of the men involved while Gray put a hand on Natsu's shoulder to keep him from following.

"Dude, what's it matter? It's just a box with a weird-looking logo. The old bastards probably won't find anything inside other than a kid's old trading card collection."

"I found it," Natsu said. "It's mine." It was more than that, though, and Natsu could tell he was doing a poor job of convincing Gray otherwise. Maybe it was nothing more than morbid curiosity, but Natsu _did_ want to know what was inside the box. He just didn't want everyone _else_ knowing too.

Lewis clapped a hand on his other shoulder, his eyes following the small crowd that was convening around an old picnic table that sat in the far corner of the overhang. His expression was odd, unlike any that Natsu had ever seen come across the boy's features in the weeks they'd been working together.

"Lewis?"

But the older boy merely shot him a smirk and tapped the temples of his glasses before slinking off to join the others.

Gray and Natsu stared after him.

Natsu cocked his head to the side. "Am I wrong for thinking he's a little weird?"

"Probably leftover from whatever happened to his nose. No one can get hit that hard in the head and not be left a little scrambled."

"Nice guy though."

"Oh, totally. Lent me his pair of gloves once."

"Did you use them?"

"Gross, no. If I ever feel like sharing sweat I'll borrow something from your gym bag."

Natsu gave his friend an affronted look, followed by a deadpan, "Gross."

Gray shot him the finger before moving to stand at the edge of the concrete slab they were all gathered on, looking up at the clouds. "Looks like they're rolling out. Storm should be over soon, but the ground will be too soft to get any work done. We're probably done for the day once this lets up."

"Want me to drive home?"

"The day I let you drive my baby is the day you spit fire."

Natsu, having already known the answer, merely shrugged. "Figured I'd offer."

They found a spot nearby where no one was sitting because the wind had blown a little rain in that soaked the concrete, but it was nothing detrimental. They'd left their lunches in the back of Gray's Jeep, so they didn't have much to do other than look around. There was a small commotion breaking out on the other side of the overhang where everyone was waiting to see what was inside his box, but Natsu didn't have the heart to check it out.

"So," Gray said, picking at a callous. "You gonna tell me what's so important about this box that you were ready to throw hands with Wick?"

"You wouldn't of had to jump in."

Gray snorted, "Of course I would've jumped in. I'd just like a heads up when you feel like you're about to be a dumbass. I feel like it's common courtesy."

Natsu scratched at his arm to keep his hands busy. "I dunno, man. I know it's probably just a piece of junk, but…" he trailed off. He couldn't find the words to convey the feeling of familiarity he'd had when he first saw the symbol, not in a way that his friend would understand. Hell, _Natsu_ didn't understand it. Why should he expect Gray to?

"Well, forget them. They can keep the trash inside if that's what they really-"

But Gray was cut off as the commotion on the other side of the overhang was quickly turning into the uproar of a mob. Men were surging forward with their hands raised over their heads as they scrambled for something that neither boy could make out from their sitting position. They both shot to their feet just as something broke the link and sprinted in their direction, the figure's glasses skewed to the side of his bleeding, re-broken nose.

"Lewis?" Natsu asked, but the boy didn't answer immediately. He shoved something hard into Natsu's chest and grinned, the look almost made maniacal by the trail of blood along his hairline and the ambiance of the storm around them.

"It was my fault that everyone noticed the box to begin with," he offered his hurried explanation. "Figured it was only fair if I got it back for you. Now _go_!" He ushered both boys out into the rain and towards the parking lot. "They still think I have it. I can buy you a little time."

"It's just a damn box!" Gray yelled, but sprinted after Natsu while fumbling in his pocket for his keys.

Natsu jerked the handle and clambered inside as Gray stuffed the key into the ignition and brought the roaring engine to life.

"You're more trouble than you're worth," he groaned, once again yanking them into a hard reverse as the tires spun on the loose gravel before finding purpose.

"Remind me to thank Lewis."

"I'll do that," Gray said, rolling his eyes. "On the card, be sure to include the part where he lent me those gloves. I'm sure he'll love reading it from the hospital bed those jackasses are going to put him in over this."

Natsu pressed his nose against the window to try and make out the crowd in the dense rain, but they still stood in the cover of the overhang, not a redhead in sight.

* * *

Natsu flipped on his lamp, illuminating his room and dousing the wooden tabletop in a hazy orange glow that warmed his skin. Mindful of newly applied bandaids on his fingers, he wiped once at his tired eyes and pulled out the top drawer where he'd stuffed the box when he first got home, before Igneel could call him down for dinner and turn it into a game of Twenty Questions.

While he was still nowhere near thankful to the assholes who had knicked it from him earlier that day, at least they had broken the seal. The way the dirt was still caked around the hinges led him to believe that Lewis had retrieved it before they could open it, which would explain the mob mentality.

 _Curiosity killed the cat, temptation brought it back, and God be with Lewis should those assholes decide for a little retribution come tomorrow at work._

He took a deep breath, wiped his hands on his flannel pajama bottoms in an attempt to stall, and then braced his fingers on either side of the metal.

* * *

 **Until Next Time...**


End file.
